Hillary Clinton's classified emails contain discussions of conversations with foreign diplomats, issues with embassy security and relations with countries from Russia to China.

The broad range of information that was deemed classified by the State Department — just within the emails published by the agency to date —underscores concerns that sensitive material was routinely mishandled on Clinton's private email server.

For example, Huma Abedin, Clinton's former deputy chief of staff, forwarded a summary of a high-level Sept. 2009 meeting to Clinton in which she detailed the "embassy security issues" that were discussed.

The issues had been raised by Eric Boswell, a diplomatic security official who was later forced to resign in the wake of the 2012 terror attack in Benghazi.

Abedin was frequently involved in the transmission of classified information to Clinton, emails show.

Cheryl Mills, Clinton's former chief of staff, and Jake Sullivan, former director of policy planning, also routinely sent or received classified emails from the secretary of state.

Despite her campaign's claims that Clinton was simply a "passive recipient" of classified information, a review of her emails indicates she wrote messages that are now classified.

For example, in July 2009, she discussed relations with Russia and Afghanistan with then-Deputy Secretary William Burns in an email that has been partially classified. She also discussed her travel plans with Burns over the private network.

Other classified conversations involved one of Clinton's present Democratic challengers for president: then-Sen. Jim Webb.

As Webb traveled through southeast Asia in August 2009, Clinton and Sullivan sent each other a series of emails that are now classified before deciding they should contact the Virginia senator at Clinton's request.

Another chain indicates Mills forwarded to Clinton's private address a classified summary of Webb's meeting with Aung San Suu Kyi, an opposition leader in Burma.

Some emails indicate foreign leaders may have been aware of the private email system Clinton had established.

In November 2009, an aide to David Miliband, Clinton's British counterpart, sent from his "home account" a classified note from Miliband to Abedin in the hopes of it reaching Clinton's eyes only.

Abedin later passed the note to Clinton and indicated it was information Miliband "doesn't want to send through the system."

Clinton has admitted Abedin had a private account on the server now in FBI custody. Abedin has yet to hand over most of her official communications from her time at the State Department.

Abedin, Mills and Sullivan are each slated to appear before the House Select Committee on Benghazi for their role in the agency's handling of the attack. Mills and Sullivan will meet with the committee Sept. 3 and 4.